US Made Anodized Purple Finish T6 Aluminum Body Ultra Lightweight Proprietary Barrel Nut Included Total Weight Including Barrel Nut Is 10.8 oz M-LOK System Rail System Slides Over Barrel Nut and is Locked Up Against Receiver With 6 Screws Tight Fit Up Against Receiver, Which Allows For A Monolithic Top Rail 15″ Length Heavy Duty Internal Diameter: 1.34″